1. Field of the Invention
The present invention relates to methods for forming a thin film on a substrate. More particularly, the present invention relates to methods for forming a thin film on an integrated circuit device by providing reactants and energies in a deposition chamber.
2. Description of the Related Art
Chemical Vapor Deposition (CVD) is a popular method of material delivery for integrated circuit device fabrication because of the potential high throughput, good conformal coverage, potential for selectivity, and/or relatively low cost. In the CVD process, a precursor molecule incorporating the desired growth element is used to deliver atoms of that element to a surface. A potential precursor molecule can have such desirable qualities as a high selectivity of surface types, and the promotion of smooth conformal growth. Ideally, the precursor molecule adsorbs on the surface, diffuses, and dissociates into the growth element and other molecular fragments. These fragments desorb from the surface leaving only the growth element on the surface. For this to be the case, the precursor-surface match should be a good one and the surface temperature should be above the precursor dissociation temperature but below the dissociation temperature for its fragments.
It may be desirable for a dielectric layer formed on an integrated circuit device to have a high capacitance. The dielectric layer may be uniformly formed to reduce or prevent defects from occurring therein. Thus, it may be desirable for the dielectric layer to have excellent step coverage and uniformity. A dielectric layer formed through a typical CVD process or a typical physical vapor deposition (PVD) process may have inferior step coverage because the PVD process thermally provides reactants to a substrate. Moreover, the dielectric layer formed by the CVD process may have a difficulty in controlling of step coverage because the CVD process simultaneously uses a plurality of reactants. As a result, a thin film, such as the dielectric layer, formed through the PVD process or the CVD process may have low reliability.
Recently, methods for forming a thin film having improved step coverage and uniformity have been produced by an epitaxial growth process, a cyclic CVD process, a digital CVD process and an advanced CVD process. However since the formation of the layer by the epitaxial growth process may take for a long time due to the growth of the molecular units, it may be undesirable to employ the epitaxial growth process in integrated circuit fabricating processes.
Atomic layer chemical vapor deposition (AL-CVD) or atomic layer deposition (ALD) can also used for depositing thin films. ALD is similar to CVD except that the substrate is sequentially exposed to one reactant at a time. ALD is performed by introducing a first reactant on to a heated substrate whereby it forms a monolayer on the surface of the substrate. Excess reactant is pumped out. Next a second reactant is introduced and reacts with the first reactant to form a monolayer of the desired film via a self-limiting surface reaction. The process may be self-limiting since the deposition reaction halts once the initially adsorbed (physi- or chemi-sorbed) monolayer of the first reactant has fully reacted with the second reactant. Finally, the excess second reactant is evacuated. The above sequence of events comprises one deposition cycle. The desired film thickness is obtained by repeating the deposition cycle the desired number of times.
In contact-heating methods used in the typical CVD and ALD processes, a substrate is heated to form a layer on the substrate. Problems may occur with these processes because the temperature of the substrate may not be readily controlled according to a temperature of reactants in the contact-heating method. This lack of control may be due to the problems associated with transmitting a heat to the substrate. Thus, the substrate may be subject to various delays due to changes in the temperature as it is moved from one deposition chamber to another when multi-layer films are formed. The additional deposition chambers may also drive up the costs of producing a multi-layer film.
Additionally, methods that can reduce the time for controlling a reacting temperature have been studied. A method for controlling the reacting temperature in an ALD process is disclosed in U.S. Patent Publication No. 2002/0066411 (hereinafter the '66411 Application). The '66411 Application utilizes a single, fixed substrate temperature setpoint as the principal means of controlling or driving the deposition reaction. The '66411 Application does this by allowing one part of the ALD process sequence (e.g., adsorption of the first reactant) to occur at a first temperature, generally lower, while allowing another part of the ALD process sequence (e.g., reaction between the second reactant with the adsorbed first reactant) to occur at a second temperature, generally higher). The '66411 Application allows for the first temperature chosen to be a lower level such that decomposition or desorption of the adsorbed first reactant does not occur, and the second temperature can be chosen to be of a higher level. Unfortunately by rapidly heating the substrate, the speed for cooling the substrate may not be as controllable which may lead to errors in the deposition process.
A method for forming a thin film using a microwave has been disclosed in Korean Patent Laid Open Publication No. 2002-0091643. This application discloses a thin film that may be formed on a substrate at a relatively low temperature. The substrate is also directly heated so that time for cooling the substrate may be too long. Moreover, a single layer may be only formed in a single chamber under this method. In other words, although time for heating a substrate may be reduced, time for cooling the heated substrate may be conversely increased. Additionally, the number of chambers may increase proportional to an increased number of kinds of layers. As a result, the unit cost of an integrated circuit device may increase due to the decrease of the efficiency in integrated circuit fabrication.